Electrode for use in electrothermal processes for the production of carbon black



I Patented Jan. 14, .1936

PATENT OFFICE ELECTRODE FOR USE IN ELEOTROTHER- MAL PROCESSES FOR THE PRODUCTION OF CARBON'BLACK John J. Jakosky, Los Angeles, Calif., assignor to Electroblacks, Incorporated, Culver City, Calif., a corporation of Nevada No Drawing.

3 Claims.

This invention is directed to an advantageous type of carbon electrode, and more particularly r to an electrode having characteristics which make it advantageous for use in certain electrothermal reaction processes such as in the eleotrothermal dissociation of organic liquids to form carbonblack.

In the production of'carbon-black by electrothermal dissociation of organic liquids after the manner set forth in United, States Patents-to Jakosky No. 1,597,277, Jakosky No. 1,673,245 and No. 1,872,297 and Jakosky et al. No. 1,912,373 and No. 1,931,800, difficulties have been experienced in the production of carbon-black which is free of carbon particles of macroscopic'proportions.

As is well known, carbon-black finds its principal use as a filler in rubber compounding, and the particular advantage of carbon-black for this purpose appears to lie in its extremely fine subdivision. It is apparent, therefore, that the presence in a carbon-black of any appreciable quantity of material which fails to be properly dispersed to microscopic or sub miscropic propor-- tions by the ordinary milling procedure in rubber manufacture, is of serious disadvantage.

It has been noted that carbon electrodes used in such eleotrothermal dissociation processes are subject to uneven arc erosion, that is, subject to pronounced pitting over the arcing surface. The degree of pitting varies with different compositions of electrodes but all available electrode materials show such pitting to some degree. It has been found that such pitting causes portions of the electrode material to be broken-away from the electrode body and disseminated into the surrounding organic liquid, and due to the fact that such broken away portions are fragments of macroscopic proportions, their presence is detrimental unless they are of such character as to be readily milled into a rubber mix. The conventional carbon electrode, being designed for a materially different use, is very hard and dense, and

therefore is not at all susceptible to subsequent 4r dispersion by such milling procedure.

The presence of the macroscopic particles in a carbon-black produced by methods involving electrothermal dissociation of organic liquids as described in the above-mentioned patents, appears 50 to also be due in large part to the formation of sol-called carbon trees which build up on, the surface of the electrode. parently formed of microscopic or sub-microscopic carbon particles which have been cemented 55 or otherwise bonded togetherto form aggrega- These trees are ap- Application August 20, 1934, Serial No. 740,637

tions which are not to any appreciable extent dis"- persible in rubber milling.

The carbon trees thus formed are actually aggregates of carbon particles having microscopic or sub-microscopic dimensions bonded together so intimately as to substantially resist the dispersing action of a rubber mill. Experimental investigation of the problem indicates that these 7 particles start as very minute deposits on the electrode surface, being possibly cemented to the electrode surface by the action of the electric arc in the formation of a coke-like material from a particular constituent of the organic liquid undergoing dissociation. The minute coked particles which adhere to the electrode surfaces provide starting points for further agglomeration and cementing of additional carbon particles and thus facilitate the formation of rather large-size aggregate or trees, some ofwhich may reach one-half inch or more in length. These carbon trees apparently grow until they are knocked off of the electrode surface and. are picked up by the liquid surrounding such electrodes. Furthermore, when these trees are dislodged they may also carry with them, mechanically, adhering fragments of the electrode materialitself.

The presence of such macroscopic carbon particles has long been recognized in the art, but heretofore the energies of investigators have been directed toward minimizing and eliminating the formation of such particles by using constantly changing arcing surfaces. Careful control of the operation of carbon-black treaters has resulted in a material reduction in the quantity of such macroscopic particles, but it is now found that the character of the electrode material and the electrode surface plays an important part in the formation of these macroscopic particles.

In view of the above, therefore, one of the principal objects of the present invention is to provide an electrode useful as an arcing element in" the eleotrothermal production of carbon-black by dissociation-of carbon-bearing liquids, of such character as to minimize the production of macroscopic carbon particles in such a' carbonblack.

A further object of the invention is to provide an electrode for the above-specified purpose which is formed of a materialwhich is in itself susceptible to dispersion in rubber milling.

A further object of the invention is to provide an electrode surface for the purpose above set forth which will prevent the formation of dimcultly milled aggregates of carbon-black.

According to the present invention, the electrode material is preferably of such nature as to be of itself easily dispersible under the action of a rubber mill, so that any particles which are broken away from the electrode body either co- 5 incidentally with the washing away of a deposited carbon particle or at other times due to other causes, such as a result of pitting, will be of such nature as to freely mill into a rubber mix according to the customary milling procedure. As a further feature of the present invention, an electrode material is provided which'is of such a nature that there is little tendency for any adhering carbon particles to build up to any appreciable size, the electrode material being of such nature-that the deposited carbon particles do not strongly adhere to the electrode and are consequently washed from the surface thereof by the action of the arc and/or the circulating submerging liquid before they have had an opportunity to grow to any appreciable dimensional proportions.

I have found that a highly advantageous electrode for the present use maybe made principally or substantially wholly of carbon-black itself, suitably bonded through the agency of a bonding or cementing material such as tar, pitch or mixtures thereof and properly dried and baked to give amodicum of physical strength to the electrode which will enable it to be handled and used without excessive breakage, but which will at the same time be of a nature such that particles thereof may, if broken-away from the electrode surface and distributed with the carbonblack produced in the electrothermal reaction, be easily milled into a rubber mix along with such produced carbon-black in the compounding of rubber. Other bonding agents are also useful in forming the carbon-black electrode of the present invention, such as sugar solutions or other syrups, water soluble gumsi such as gum arabic,--agar-agar or the like, or resins, gum resins or the like.

Previous to the present disclosure, electrodes for electric arcs have been made of one or another form of carbon thoroughly bonded so that a hard electrode material is realized and while the prior art shows that lampblack has been employed in the production of arc carbons the only successful electrodes containing lampblack were those which also contained a relatively large proportion of a suitable coke or other form of hard carbon, the mixture being thoroughly baked to obtain the desired flint-like electrode material. To the best of applicant's mowledge no electrode has been hitherto proposed which is in itself sumciently soft and friable to fulfil the objects of the present invention, this type of electrode being entirely contrary to the established practice of electrode manufacture. As a specific example of preparation of an electrode according to the present invention, I may mix carbon-black with a suitable proportion of binding material such as coal tar residue, pitchor other comparable material in solution in a suitable solvent medium such as benzene, thoroughly intermixing the above ingredients to obtain a homogeneous semi-plastic mass. This mass may then be formed into the desired electrode shape under pressure or by extrusion as desired, the electrode suitably dried at a relatively low temperature to remove the principal proportion of the solvent material and subsequently baked to a suificient temperature to cause the binding material to cement the par- 5 ticles of carbon-black together. The relative proportion of carbon-black and binding material, as well as the drying. and baking temperatures and time, are subject to variation, depending upon the type and characteristics of the binding ma- 10 terial employed, and it will be appreciated that in any event the proportions and baking conditions are so selected as to provide a bonding of the carbon-black particles into an integral electrode body of such character as to provide the 15 above-described dispersibility in a rubber mix, during a milling operation, of any fragments thereof which may have been loosened from the electrode body during the use thereof in the production of the carbon-black used in said rubber 20 mix. While the above type of electrode is not as resisistant to are wear as are the customary coke or graphite electrodes hitherto employed for the purpose, they are greatly to be preferred in view of their physical characteristics. 25

It will be appreciated that the electrode of the present invention may be made of any desired shape, according to the teaching of any of the above-mentioned patents. They may be made of ring-shape, disc-shape, rod-shape, or of any other 30 useful shape. In the teaching of the above patents, the electrodes are mounted in a closed reaction chamber provided with means for maintaining a body of dissociable carbon-bearing liquid in said chamber, and the electrothermal 35 reaction is realized by maintaining one or more arcs between said electrodes beneath the surface of said liquid body, that is, with the electrodes submerged in the liquid at the vicinity of the arc. The are zone is thus continually supplied 4,0 with dissociable liquid, and the desired carbonblack is immediately disseminated into the surrounding liquid medium.

' I claim:

1. An electrode, for use in the electrothermal as dissociation of organic liquids to form carbonblack, containing carbon-black as its principal constituent and characterized by being easily dis- I persed in a rubber mix by the ordinary rubber milling procedure. 50

2. An electrode, for use in the electrothermal dissociation of organic liquids to form carbonblack, consisting principally of carbon-black and a binding agent and formed into an integral structure of a soft and friable nature, character- 55 ized by being easily dispersed in a rubber mix by the ordinary rubber milling procedure.

3. An electrode, for use in the electrothermal dissociation of organic liquids to form carbon-, black, in which electrodes are employed in sub- Gt merged relation to such liquids, characterized by being soft and friable in nature whereby disintegration of such electrode in the dissociation operation will result in the dissemination of electrode particles within such liquid which are easily as dispersed in a rubber mix by the ordinary rubber milling procedure, and containing carbonblack as its major constituent.

JOHN J. JAKOSKY. 

